tetranor-PGDM is a major metabolite of prostaglandin D2 (PGD2) found in human and mouse urine.1 In human urine, tetranor-PGDM is significantly more abundant than the PGD2 metabolites 11β-PGF2α and 2,3-dinor-11β-PGF2α and is the only endogenous PGD2 metabolite detectable in mouse urine by LC-MS. Normal levels of tetranor-PGDM in human and mouse urine are 1.5 ng/mg creatinine and 8.1 ng/mg creatinine respectively.1 Cayman’s tetranor-PGDM ELISA Kit is a competitive assay that can be used for quantification of tetranor-PGDM in urine. This assay converts tetranor-PGDM to a stable derivative, tetranor-PGJM, that can be easily quantified. The assay has a range from 6.4-4,000 pg/ml and a sensitivity (80% B/B0) of approximately 40 pg/ml.